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Should've done a pre-teardown leakdown test. Could've told you what it needed. I do that in any motor that's coming apart for just a refresh as opposed to a rebuild.
I'm more inclined to just lap them and let it ride and put the money towards more important things like bearings. The motor was running strong before I tore it down so I'll be happy as long as it stays together next season.
Marc, I don't think it's fuel related since the intake valves had zero rust on them. Their contact faces were also in much better shape. Which is to be expected.
Originally Posted by letsgetthisdone
Probably from sitting and the stock seats are ferrous.
Yes I'm pretty sure it's from the seats. Our stock exh valves are inconel (confirmed it with a magnet) and inconel doesn't really rust much at all (depending on the grade) but the seats are probably powdered metal which rusts like any other iron base alloy does.
I shot some pictures over to some old coworkers who build IMSA racing engines to see what they think. They said it's possible the pitting is great enough that the valve couldn't transfer heat to the head well enough and overheated and compounded the issue on itself. Still waiting to hear what their final verdict is tho.
You'll be hard pressed to get a race engine builder to tell you to reuse just about anything that shows wear...
I know a guy that works at Kroyer and builds trophy truck motors, everything is replaced at a certain mileage interval. Engines are torn down and gone through every 1500 miles. Parts at their mileage limit are replaced, as well as anything that looks abnormal, along with new rings and bearings. It's what it take for an engine to survive a real racing environment, something that our 20-30 minute HPDE sessions can't shake a stick at...lol
Oh yea, I'm well aware haha. The IMSA engine program they have does the same stuff. Cylinder heads are **** canned after the second rebuild regardless of how they look. We used to get a lot six digit paperweight motors back.
But these guys are hotrod guys too and are familiar with most engines under the sun so their advice is always pretty good.
Some of it was ridiculous tho. Like when I was working there and the program first came in, the rebuild book that VAG had made for the engine didn't saying anything about bearing clearances. It said if the crank journal measures X you use Y color bearing but didn't actually say what size each color was or where it would leave your clearance at. So needless to say it was pretty easy to give them some better quality haha.
That's how a lot of OEM's are. Mitsubishi is the same way. They stamp the block, the crank, and the rods for what size it is. The tunnel size + journal size = this color bearing lol
They do give clearance to check with plastigauge though.
Decided to pick up one of those Blox cam gears on amazon and it's the real deal, even had blox stickers on the box. Looks like a quality piece and I have no clue how they're selling them this cheap.
GSC S2's or Kelford 272's would be smidge bigger but they're readily available and I doubt you'd see any losses anywhere.
Because I'm a cheap f*** lol. The FP4 grind doesn't seem must less aggressive than those either and since they're ground by Comp the grind sheets are available.
The GSC and Kelford stuff tends to hold a premium over other grinds because they're the go to options. I've seen a few sets of the FP cams sell for under $200 over the past couple months. That $300-400 saved pretty much covers a valve job.
